1. Field of the Invention
The present invention relates to a method for replenishing processing chemicals, for example, a developing agent, and also relates to a photographic printer such as a digital photographic printer. More particularly, the present invention relates to a method for replenishing a developing agent in a digital photographic printer in which an image is exposed onto a photosensitive material on the basis of digital data including image data and the exposed photosensitive material is developed by a developing agent, and also relates to the digital photographic printer.
2. Description of the Related Art
The term "image rate" used in the specification of the present invention means a parameter which is used to obtain, based on a density characteristic value of an image, image density, image contrast, and the like, a quantity of a developing agent replenished, the developing agent being used for development processing of the image. Further, the term "print image rate" used in the specification of the present invention means a parameter which is used to obtain a quantity of the developing agent replenished on the basis of a density characteristic value of the image among the image rate.
Conventionally, a method for replenishing a color development processing solution (hereinafter referred to as a "developing agent") in a development processing section of a projective photographic printer in which a general silver halide photosensitive material is used (for example, a printer in which exposure is effected in such a manner that light from a light source is irradiated on a negative film and the transmitted light is projected on a photographic printing paper via a lens) is constructed such that, assuming that an image modulus of an exposed image is set substantially fixed, the amount of consumption (i.e., a quantity of the developing agent to be replenished, hereinafter referred to as "replenishment quantity") is calculated by multiplying a processing quantity (i.e., a processing area) by a fixed coefficient, and on the basis of the calculated quantity, a replenishing agent of the replenishment quantity is supplied. Namely, an image exposed by the projective photographic printer is one in which objects in the natural world are photographed, and it can be supposed that a density characteristic value of the image, image density, image contrast, and the like will be generally stabilized. Accordingly, it can be further supposed that the image rate of such an image will become substantially constant. As a result, the above-described replenishment quantity calculation method can be applied to the projective photographic printer.
Further, in recent photographic printers, various images are to be processed, such as an image with an original image to be printed being recorded on a negative film or on a slide, an image recorded on a photographic print, and digital image data stored on a storing medium such as a floppy disk. Accordingly, the present inventors have proposed a printing system (corresponding to the above-described photographic printer) in which an exposure section is provided correspondingly for each type of original image and a photosensitive material on which an image is exposed in any one of the exposure sections is subjected to development processing in a common development processing section (see Japanese Patent Application Nos. 6-310598 and 6-310599). It can be supposed that, among original images processed by the above-described photographic printer, an image recorded on a negative film or on a slide has a substantially fixed image rate, the above-described replenishment quantity calculation method can be applied.
On the other hand, in recent years, there has been widely used a digital photographic printer which has a function of exposing, onto a photographic printing paper, an image generated by computer processing, for example, computer graphics (hereinafter referred to as CG), a composite image (for example, an image formed with a plurality of images being synthesized on a mount paper such as an album print, or an image with characters and a photograph being synthesized), and the like. The above-described CG images, composite images, or the like, exposed by the digital photographic printer, have different densities (for example, there are various images which are extremely dark, extremely light, and the like) unlike images, with objects in the natural world being photographed, exposed by the above-described projective photographic printer. Therefore, it cannot be supposed that the image rate of the above-described CG image or composite image becomes substantially constant.
Accordingly, in a case in which the above-described replenishment quantity calculation method is applied to the digital photographic printer, an appropriate replenishment quantity cannot be calculated due to each image rate in the images printed by the digital photographic printer being not made constant. When a developing agent of an inappropriate replenishment quantity is supplied, over-replenishment or under-replenishment occurs so that a fixed development processing condition cannot be maintained. As a result, there is a possibility that a finished state of a photographic print may be adversely affected by the above circumstances.
In other words, there has not been established, under existing circumstances, a developing agent replenishing method in which, in a photographic printer for effecting exposure and development processing for various original images, an appropriate replenishment quantity of the developing agent is calculated for each of the various original images, and on the calculated replenishment quantity, proper replenishment of the developing agent is effected.
Further, there has been recently a growing need for apparatus downsizing and a downsized development processing tank or reduced replenishment quantity of the developing agent is required. At the same time, precise control of the replenishment quantity of the developing agent is also required.
In order to solve the above-described drawbacks, there has been proposed a technique in which, by effecting prescan photometric processing using a sensor for a character document or an original document with a plurality of prints installed on a mounting paper and by supposing an image rate of an image to be printed on a photographic printing paper based on the photometric value and a density correction key, an optimum replenishment quantity is calculated by multiplying a parameter varying in accordance with the image rate by a processing quantity, and based on the calculated quantity, the developing agent of the optimum replenishment quantity is supplied (see Japanese Patent Application Laid-Open (JP-A) No. 2-146038).
In the digital photographic printer, both an original such as a negative film is printed by photometric processing (scanning) using a sensor, and digital image data generated by computer processing (for example, CG image), digital image data previously read by another scanner so as to be stored in a storing medium, and the like may be printed.
However, the prescan photometric processing using the sensor is not intended for the above-described digital image data, and therefore, the above-described developing agent replenishing method disclosed in JP-A No. 2-146038 cannot be applied to the digital photographic printer. In addition, these digital image data particularly have different densities (for example, various image data extremely dark, extremely light, and the like) and it was difficult to assume that the image rate becomes constant. Namely, in the development processing for the above-described digital image data generated by computer processing, digital image data stored in a storing medium, and the like, it was difficult to calculate an appropriate replenishment quantity of the developing agent.